1. Field of the Invention
The present invention relates to solar energy collectors, and more particularly to trough-type collectors having reflective surfaces internally of the trough for focusing sun's rays entering the trough onto a radiation receiver. The present invention is particularly suitable for fixed installations, that is, for stationary mounting which does not track the apparent motion of the sun.
2. Description of the Prior Art
It has previously been known to collect solar radiation in trough shaped apparatus lined with reflecting surfaces and arranged to concentrate or focus solar radiation entering the trough upon a receiving structure such as heat exchangers, thermoelectric devices, photoelectric devices, and the like. Such troughs are usually of semi-cylindrical configuration or of V-shaped cross section.
It has been proposed to make a trough-shaped solar concentrator utilizing a transverse plan profile curve in the form of spaced double parabolas having focus at the opposite edge of the exit aperture and axis of parabola inclined at an angle .theta..sub.max with respect to the optic axis (see "Principles of Solar Collectors of a Novel Design" by Roland Winston, published in Solar Energy, Volume 16, pages 89-95, by the Pergamon Press, 1974, printed in Great Britian).
Some of the known trough-type collectors, of whatever cross sectional profile, have reflective ends and others have open or transparent ends. None of the prior art makes one end transparent for admitting sunlight which otherwise would be blocked off by a closed end and at the same time makes the opposite end capable of reflecting back into the trough sunlight which otherwise would not be so reflected.